JP4264269B2 - Hydrophilic tube and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrophilic tube and a method for producing the same, and more particularly to a hydrophilic tube and a method for producing the same that can naturally and easily remove bubbles mixed in the tube.
[0002]
[Prior art]
Elastomer tubes are used in various fields, and when liquids are sent using such tubes, it is often required to remove mixed bubbles. However, especially when air bubbles are mixed in a thin tube, it may not be easily removed, and a troublesome air bubble removal operation may be required.
[0003]
For example, in the medical field, tubes made of elastomer are used for administration of infusions and drug solutions. However, when setting a tube to an infusion device, etc., bubbles are mixed in the tube, or there are no bubbles when setting. However, bubbles may be generated in the tube due to changes in temperature. In order to prevent air bubbles mixed in the tube from being sent into the body together with the infusion solution or drug solution, the flexible tube is flicked with a finger or given vibration before administration of the infusion solution or drug solution. It tries to remove the air bubbles that exist inside, but it forces nurses and others to take a lot of trouble and troublesome work. In particular, tubes used in pediatrics have thin tubes with an inner diameter of about 3.5 mm, 3 mm, 2 mm or less (for example, about 1 mm for special applications), which makes air bubble removal more troublesome. ing. Also, careful attention is required to find out that minute bubbles are present and to confirm that the bubbles have been extracted.
[0004]
As a technique related to the present invention, Patent Document 1 discloses a medical tube in which a titanium oxide photocatalyst layer is provided on a tube made of a flexible elastomer and has antibacterial properties, and a method for manufacturing the medical tube. However, in the technique described in Patent Document 1, although it is possible to give the medical tube favorable antibacterial properties, it is not possible to provide the above-described bubble extraction performance, but rather, a titanium oxide photocatalyst layer is provided. This tends to make it difficult for bubbles to be extracted. This is found in the examination process of the present invention to be described later, but various additives are usually added to the material made of elastomer in order to ensure flexibility, and these additives are used as a photocatalyst layer. It is considered that the surface layer is hydrophobized rather than being hydrophilized, and the bubbles are difficult to escape from the inner surface of the tube, and the bubbles are difficult to escape. It is done.
[0005]
Also, as a hydrophilization treatment, other than elastomer, plasma treatment method, chemical treatment method, physical roughening method, ultraviolet ray and radiation treatment method, flame treatment method, graft polymerization method, coupling agent treatment method Various processing methods are known. For example, when polyethylene terephthalate is treated with sodium, the contact angle of water is 40 degrees or less, when polyester is glow discharge treated, it is 5 degrees or less, when polyethylene is plasma treated, it is about 20 degrees, and with polyacrylamide grafted polyethylene, it is about 10 degrees. In addition, it is known that when polystyrene is irradiated with ultraviolet rays, each of them can be hydrophilized to about 30 degrees. However, in both cases, the target of hydrophilization is not an elastomer but a hard base material.
[0006]
[Patent Document 1]
JP 2001-178825 A (Claims)
[0007]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to form a tube inner surface with a specific surface layer, particularly for a tube made of an elastomer that is required to remove air bubbles, so that air bubbles can easily and preferably naturally escape from the tube. The present invention provides a hydrophilic tube and a method for producing the same.
[0008]
[Means for Solving the Problems]
  In order to solve the above problems, the hydrophilic tube according to the present invention is:Silicone rubber from which low molecular weight polydimethylsiloxane has been extracted and removed using a mixture of n-hexane and acetoneOn the inner surface of the tube body consisting ofIt consists of a layer containing titanium oxide as a photocatalyst and subjected to light irradiation treatment,A hydrophilic layer having a contact angle with water of 20 degrees or less is provided.Hydrophilic tube with an inner diameter of 2 mm or lessConsists of.
[0009]
This hydrophilic layer can also be specified in terms of the ease of escape of bubbles present in the tube, particularly in relation to the above-mentioned problem of the present invention. For example, as the hydrophilic layer, when the tube is tilted from the horizontal in a state where the tube is filled with water and a bubble having a size of 2 μL contacting the inner surface of the tube is present in the filled water, It is preferable that the easy bubble detachment index represented by the tube inclination angle starting to rise along the inner surface is composed of a layer of 20 degrees or less. That is, as is clear from the results of various tests described later, the hydrophilicity of the inner surface of the tube (which can be expressed by the contact angle with water) and the ease of escape of bubbles from the tube correspond very closely. In addition, if the contact angle of the inner surface of the tube with water is set to a specific value or less, the easy bubble separation index can be suppressed to a specific value or less, and excellent ease of bubble removal can be obtained.
[0012]
Although the above-mentioned easy bubble separation index is defined for a bubble having a size of 2 μL, in reality, bubbles of various sizes are mixed, and the ease of escape varies depending on the size of the bubble. In addition, the ease of bubble removal varies depending on the relative size relationship between the bubble size and the tube inner diameter, especially when the bubble diameter is larger than the tube inner diameter and the bubble is deformed vertically in the tube longitudinal direction. If the liquid above the bubble does not move below the bubble, the bubble is unlikely to rise and escape. In the case where such large bubbles are likely to be generated, it is particularly preferable that at least one ridge or groove extending in the longitudinal direction of the tube is provided on the inner surface of the tube. By adopting such a configuration, the liquid above the bubbles can easily move below the bubbles along the ridges or dents on the inner surface of the hydrophilic tube, and the bubbles rise easily. And extracted. For example, a thin ridge extending in the tube longitudinal direction may be formed on the inner surface of the tube as the ridge, and a groove extending in the longitudinal direction of the tube may be formed on the inner surface of the tube, for example. A plurality of these ridges or grooves can be provided as necessary.
[0013]
  The inner diameter of the tube in the present invention is,In general, a thin tube is more difficult to remove air bubbles, and the work of extracting air bubbles becomes more difficult.InTube with an inner diameter of 2 mm or lessIs targeted.Especially for medical tubes, the inner diameter is about 3.5 mm or less,EspeciallyIn many cases, it is desired to facilitate the extraction of bubbles from a tube having an inner diameter of 2 mm or less.
[0014]
In addition, the present invention can provide a desirable effect when applied to a medical tube in which air bubble extraction is a problem at present in terms of usage. Examples of the medical tube to be applied include an infusion tube or a drug solution administration tube, a human body insertion or indwelling catheter, and the like. Of course, the present invention can be applied to tubes in various industrial fields in addition to medical tubes, particularly those that are required to easily remove bubbles. For example, when high-speed chromatography is operated for a long time by automatic sampling, bubbles are likely to be mixed in the portion where the pump sucks up the mobile phase (liquid). However, if bubbles are mixed, stable flow of the mobile phase is hindered and quantitative performance is reduced. Since problems arise, it is necessary to remove air bubbles. Even in such a case, the hydrophilic tube according to the present invention is effective, and bubbles can be easily removed.
[0015]
  The method for producing a hydrophilic tube according to the present invention includes:Silicone rubber from which low molecular weight polydimethylsiloxane has been extracted and removed using a mixture of n-hexane and acetoneOn the inner surface of the tube body consisting ofIt consists of a layer containing titanium oxide as a photocatalyst and subjected to light irradiation treatment,A hydrophilic layer having a contact angle with water of 20 degrees or less is formed.Method for producing hydrophilic tube having an inner diameter of 2 mm or lessConsists of.
[0016]
In this method of manufacturing a hydrophilic tube, the tube was tilted from the horizontal as a hydrophilic layer with the tube filled with water and air bubbles having a size of 2 μL in contact with the inner surface of the tube in the filled water. It is preferable to form a layer having an easy bubble detachment index of 20 degrees or less, which is represented by a tube inclination angle that sometimes starts to rise along the inner surface of the tube.
[0019]
As described above, when it is required to remove particularly large bubbles, it is preferable to further form at least one ridge or groove extending in the longitudinal direction of the tube on the inner surface of the tube.
[0020]
  The present invention is particularly effective for a tube having an inner diameter of 2 mm or less.For this reason, this size tube is the target.
[0021]
The tube to be applied is, for example, a medical tube, and examples of the medical tube include an infusion solution or a drug solution administration tube and a human body insertion or indwelling catheter. It can also be applied to tubes in other fields such as for high-speed chromatography.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail together with preferred embodiments.
First, the examination process that led to the completion of the present invention will be described, and each examination item and examination result will be described later.
[0023]
[Proceedings to the completion of the present invention]
(1) First, in order to make it easier for bubbles to escape from the tube made of elastomer as the starting point of the idea, if the inner surface of the tube is made hydrophilic and the liquid is easily wetted and spread, it will be present on the inner surface. It was thought that the bubbles could easily escape from the inner surface and escape easily by their own buoyancy.
[0024]
(2) First, a method for hydrophilizing the inner surface of the elastomer tube was examined. In general, as an effective method for imparting hydrophilicity or superhydrophilicity to the surface of a substance, a method of forming a photocatalyst layer containing titanium oxide or the like and performing a predetermined light treatment with ultraviolet rays or the like is known. It is known that glass or the like can be made hydrophilic or superhydrophilic by this method. However, even when such a titanium oxide photocatalyst layer is simply formed on the surface of the elastomer which is the subject of the present invention, hydrophilicity is not actually expressed. For example, in Patent Document 1 described above, it is proposed to form a titanium oxide photocatalyst layer on the surface of a medical elastomer tube for the purpose of imparting antibacterial properties. In some cases, the contact angle with water did not decrease, but rather deteriorated (increased contact angle).
[0025]
(3) Next, even if a titanium oxide photocatalyst layer is formed on the surface of the elastomer targeted by the present invention, the hydrophilicity does not appear because the additive that precipitates or diffuses from the inside of the elastomer is hydrophilic. Before the formation of the titanium oxide photocatalyst layer, a test was conducted to extract and remove specific additives from the elastomer as a material so as not to inhibit the flexibility of the elastomer. It was. As a result, it was found that the hydrophilicity of the inner surface of the elastomer tube after the formation of the titanium oxide photocatalyst layer can be greatly improved by extracting and removing a specific additive. It was also confirmed that the extraction effect can be enhanced and the hydrophilic expression effect can be enhanced by optimizing the extraction agent according to the additive to be extracted. Furthermore, a forced test was conducted to observe the ease of air bubble removal using carbonated water for the elastomer tube that succeeded in hydrophilicizing the inner surface and the conventional elastomer tube that was not hydrophilicized. It was confirmed that air bubbles hardly remained in the elastomer tube.
[0026]
(4) Since we were able to find a specific method of hydrophilizing the inner surface of the elastomer tube (lowering the contact angle with water) and facilitating the removal of bubbles, the hydrophilic (contact angle with water) The relationship with ease of removal was quantified, and the degree of hydrophilicity on the inner surface of the tube was examined to be able to remove bubbles. The test for quantification is a simulation test using a glass material mainly to determine the relationship between the contact angle with water and the ease of bubble removal. Considered and tested. Also, in order to more appropriately quantify the ease of bubble removal, an easy bubble removal index indicating the ease of separation of bubbles of a specific size from the tube inner surface was defined and introduced.
[0027]
(5) As a result of these series of studies, in order to obtain the target ease of bubble removal, a hydrophilic layer having a contact angle with water of 20 degrees or less is provided on the inner surface of the tube body made of elastomer. The hydrophilic layer is preferably formed of a layer having an easy bubble separation index of 20 degrees or less, and the present invention has been completed. It has also been found that in order to actually set the contact angle of the inner surface of the elastomer tube to 20 degrees or less in this way, for example, extraction and removal of elastomer additives can be realized. Therefore, it can be seen that an elastomer tube having a target hydrophilic inner surface can be actually manufactured, and by implementing the present invention, it is an object of the present invention to allow bubbles to easily escape from the elastomer tube. Is achieved.
[0028]
The present invention will be described in detail along the course of the series of studies described above.
First, a medical tube is selected as an elastomer tube to be studied in the present invention. At present, silicone rubber is often used for insertion or indwelling in the human body, and vinyl chloride is often used. Silicone rubber used in catheters was selected as a material to be examined for hydrophilicizing the inner surface of the tube for administration of infusion solutions or drug solutions. As described above, when a titanium oxide photocatalyst layer is simply provided on the silicone rubber used in the catheter, hydrophilicity cannot be exhibited despite irradiation with ultraviolet rays. The reason why this titanium oxide photocatalyst layer does not become hydrophilic is because the additives contained in the silicone rubber constituting the catheter, especially low molecular weight polydimethylsiloxane produced by unreacted or side reaction, is the surface of the titanium oxide photocatalyst layer. Thought to be due to spreading. Therefore, the silicone rubber substrate having the same composition as the catheter is subjected to a specific treatment to extract and remove the low molecular weight polydimethylsiloxane, coated with a titanium oxide photocatalyst layer, and subjected to a predetermined light irradiation treatment to make the hydrophilic property. A test was conducted to determine whether or not the grant was possible.
[0029]
A silicone rubber substrate having a size of 10 mm × 15 mm and a thickness of 0.5 mm was subjected to reflux extraction using carbon tetrachloride for 15 hours. The treated substrate was immersed in a 5M aqueous sulfuric acid solution for 3 hours, and then ultrasonically washed with Na-free detergent for 20 minutes and then with ion-exchanged water for 20 minutes. After the water was replaced with ethanol, it was dried using a dryer. In a glove box adjusted to a relative humidity of 30% or less, a protective adhesive layer coating solution (NDC-100A, manufactured by Nippon Soda Co., Ltd.) was dip coated once on the substrate. At this time, the pulling rate from the coating tank was 15 cm / min. The coated substrate was dried at 60 ° C. for 30 minutes in an electric furnace and then left for 30 minutes to cool down sufficiently. Subsequently, after ultrasonic cleaning with ion-exchanged water for 20 minutes and drying, a titanium oxide photocatalyst layer coating solution (NDC-100C, manufactured by Nippon Soda Co., Ltd.) was dip coated once by the same operation. The coated substrate was dried in an electric furnace at 100 ° C. for 30 minutes. The substrate coated with the titanium oxide photocatalyst layer was allowed to stand overnight and irradiated with ultraviolet light (UV) using a black light (light intensity: 1 mW / cm).²). Using a contact angle meter, the change in the contact angle of water due to the titanium oxide photocatalytic activity with respect to the ultraviolet irradiation time was measured.
[0030]
In the same manner, a silicone rubber substrate having a size of 10 × 15 × 1 mm, which was not subjected to reflux extraction treatment, a silicone rubber substrate which was reflux-extracted for 60 hours in a size of 10 × 15 × 0.5 mm, 15 × 20 × 1 mm size The change in the contact angle of water was measured using a silicone rubber substrate subjected to reflux extraction treatment for 120 hours and a silicone rubber substrate subjected to reflux extraction treatment at a size of 5 × 10 × 0.2 mm for 44.5 hours. The results are shown in FIG. Note that any of the silicone rubber substrates subjected to the reflux extraction process maintained the flexibility required as a catheter.
[0031]
As shown in FIG. 1, in the untreated substrate, the contact angle decreased only to about 80 degrees even when irradiated with ultraviolet rays for 180 minutes, and there was a region where the contact angle increased rather in the middle. On the other hand, the contact angle of the substrate subjected to the reflux extraction treatment was lower than that of the untreated substrate under any condition. From this, it is considered that the unreacted low molecular weight polydimethylsiloxane could be removed by the above reflux extraction treatment.
[0032]
In addition, the longer the processing time was, the smaller the contact angle was and the more hydrophilic the substrate of 10 × 15 × 0.5 mm size was, but the substrate of 15 × 20 × 1 mm size was treated for 120 hours. It showed only a lower hydrophilicity than a 10 × 15 × 0.5 mm size substrate treated for 15 hours. Furthermore, in order to remove low molecular weight polydimethylsiloxane, the substrate of 5 × 10 × 0.2 mm size has the lowest contact angle despite the short processing time of 44.5 hours. It has been found that it is more effective to reduce the substrate size, particularly the thickness, than to increase the processing time. This is thought to be because, in reflux extraction under atmospheric pressure, carbon tetrachloride cannot penetrate deep inside the silicone rubber substrate and can only treat near the surface. When the 5 × 10 × 0.2 mm size substrate that showed the most hydrophilic property was left in a dark place for 20 hours, the contact angle was kept at a low value of 5.1 degrees.
[0033]
In this way, it is confirmed that the titanium oxide photocatalyst layer formed on the silicone rubber can be made hydrophilic by extracting and removing the unreacted low molecular weight polydimethylsiloxane from the target silicone rubber in advance. It was done.
[0034]
Next, optimization of the extractant in the extraction and removal processes as described above was studied. That is, since carbon tetrachloride is not preferable in terms of toxicity in actual processing, reflux extraction with another extractant having low toxicity was attempted. In addition, since there are many actual catheters having a thickness of about 1 mm or more, it is considered that the extraction process performed under atmospheric pressure is insufficient. Therefore, a silicone rubber substrate having a thickness of 2 mm is placed in a pressure vessel. The extract was put in and subjected to an extraction treatment under high temperature and high pressure conditions (120 ° C., about 10 atm) to examine how much hydrophilicity can be expressed. In addition, the possibility of shortening the ultraviolet irradiation treatment time and the possibility of improving the hydrophilization speed depending on the type of the extractant were also investigated. Furthermore, in order to confirm that the low molecular weight polydimethylsiloxane was removed by such an extraction treatment, the extracted liquid was analyzed by gas chromatography.
[0035]
First, acetone and n-hexane were selected as the extractant, and a substrate cut out to a length of 3 cm from a 2 mm-thick silicone rubber catheter and the extractant were placed in a pressure vessel, and the electric furnace maintained at 150 ° C. Left in for 2 hours. The substrate was taken out of the container, and after the sulfuric acid treatment and washing as in the above test, the same adhesive layer and titanium oxide photocatalyst layer as in the above test were coated. Strength of the formed titanium oxide photocatalyst layer is 1 mW / cm²The contact angle change of water was measured.
[0036]
The results are shown in FIG. The contact angle decreased slightly faster when extracted with n-hexane than when extracted with acetone. Therefore, it is considered that n-hexane is more suitable than acetone between the two extraction agents.
[0037]
Next, whether or not the low molecular weight polydimethylsiloxane considered to be extracted was surely extracted and removed by reflux extraction as described above was confirmed by analyzing the extract with gas chromatography.
[0038]
In a pressure vessel, 4 silicone rubber substrates cut into a length of 3 cm from the catheter and 40 mL of n-hexane were placed and left in an electric furnace maintained at 150 ° C. for 2 hours. When the extract was analyzed by gas chromatography, it was confirmed that a large amount of low-molecular-weight polydimethylsiloxane was contained, and in addition, it was confirmed that various additive components were also contained. Thereafter, the substrate was extracted again at 150 ° C. for 2 hours. When the second extract was analyzed by gas chromatography, it was confirmed that the content of the low molecular weight polydimethylsiloxane was significantly reduced compared to the first.
[0039]
Further, the first and second extraction liquids were each dropped onto a glass substrate that had been superhydrophilized by coating with titanium oxide to make it hydrophobized, and then strength 1 mW / cm.²Was irradiated for 1 week, and the change in contact angle was measured. As a result, as shown in FIG. 3, since the extract was hydrophobized when dropped onto the superhydrophilic titanium oxide photocatalyst layer and dried, the low molecular weight polydimethylsiloxane was indeed a causative substance for inhibiting hydrophilization. Was confirmed. Moreover, when the ultraviolet rays were irradiated for 1 week, the first extract was not hydrophilic at all, but the second extract was superhydrophilic. This is because if a large amount of polydimethylsiloxane is contained as in the first extract, decomposition with titanium oxide becomes difficult, and even if the amount of polydimethylsiloxane is very small as in the second extract. For example, it is considered that the decomposition action has progressed and super hydrophilicity has been shown. This also confirms that low molecular weight polydimethylsiloxane is indeed a causative substance for inhibiting hydrophilization.
[0040]
Thus, when the elastomer tube material is silicone rubber, the low molecular weight polydimethylsiloxane is first extracted and removed, and a titanium oxide photocatalyst layer is formed on the treated silicone rubber to increase the contact angle with water. It has been found that it can be lowered and made hydrophilic. As the extractant, it was confirmed that acetone or n-hexane can be used, but in order to search for a more optimal extractant, a mixed solution of acetone and n-hexane was tested as an extractant.
[0041]
  Similar to the above test, a silicone rubber substrate cut into a length of 3 cm from the catheter, 20 mL of n-hexane and 20 mL of acetone were placed in a pressure vessel and left in an electric furnace maintained at 150 ° C. for 2 hours. The substrate is taken out from the container, and the adhesive layer and the titanium oxide photocatalyst layer are coated as in the above test, and the strength is 1 mW / cm.²The change in the contact angle of water was measured by irradiating UV rays. For comparison, a test using only n-hexane was similarly performed. As a result, as shown in FIG. 4, in the case of using only n-hexane, the rate of decrease in the contact angle is fast for about 2 hours after the ultraviolet irradiation, but after that, the rate of decrease becomes dull and eventually 24 hours later. It decreased only to about 15 degrees. On the other hand, in the mixed liquid of n-hexane and acetone, the rate of decline is slow at the beginning, but it decreases smoothly from about 1 hour after irradiation to about 8 hours, and after 24 hours it is 4.9 degrees and is extremely hydrophilic. Expressed sex. As a result, it was found that a specific extract composed of a mixture of n-hexane and acetone is extremely effective for extracting and removing a specific additive from silicone rubber.Therefore, this invention prescribes | regulates using the extractant which consists of this liquid mixture of n-hexane and acetone as a requirement.
[0042]
Next, the titanium oxide photocatalyst layer coated on the inner surface of the silicone rubber catheter from which the specific additive is extracted and removed as described above, and the light irradiation treatment can certainly improve the ease of air bubble removal, It was observed by the test.
[0043]
As described above, an adhesive layer (NSC-200A manufactured by Nippon Soda Co., Ltd.) and an inner surface of a silicone rubber catheter obtained by extracting and removing a specific additive component using n-hexane in a pressure vessel A titanium oxide photocatalyst layer (NRC-300C, manufactured by Nippon Soda Co., Ltd.) was dip coated and dried in an electric furnace. UV light (strength: 1 mW / cm) on the titanium oxide photocatalyst layer²) To make it hydrophilic. A test in which carbonated water is poured into a glass cup coated with titanium oxide, and the catheter and a catheter not formed with a titanium oxide photocatalyst layer are placed therein, and bubbles are forcibly attached or present in each catheter. Went. Since the titanium oxide-coated glass cup is hydrophilic when exposed to ultraviolet light, bubbles do not adhere to it, and through the transparent glass cup, it was possible to observe the state of bubble attachment inside each accommodated catheter. .
[0044]
The results are shown in FIG. The right side of FIG. 5 shows a catheter having a hydrophilized titanium oxide photocatalyst layer, and the left side shows a catheter having no titanium oxide photocatalyst layer formed. As a result of observation, it was confirmed that in the catheter whose inner surface was made hydrophilic, it was clearly difficult for bubbles to adhere and easily escape.
[0045]
In this way, it was confirmed that hydrophilizing the inner surface of the elastomer tube was effective for facilitating air bubble removal, and a specific technique for actually hydrophilizing the inner surface of the tube was found. An attempt was made to quantify the relationship between the hydrophilicity (contact angle with water) on the inner surface of the tube and the ease of bubble removal, and the degree of hydrophilicity that should be provided was investigated.
[0046]
In the test for quantification, regardless of the material of the base material, the hydrophilicity of the surface, that is, the relationship between the contact angle with water and the ease of bubble removal at the contact angle should be determined. The simulation test was performed using a glass tube.
[0047]
In the test, as shown in FIG. 6, water was put in the container 1, and the transparent glass tube 2 having a predetermined inner diameter was inserted therein so that the water was filled to a predetermined height. From the lower end of the glass tube 2, the air in the syringe 3 was expelled by using the bubble injection syringe 3 whose volume can be accurately determined, thereby injecting it into the glass tube 2 as bubbles 4 having a predetermined volume. As the glass tube 2, a glass tube having an inner diameter of 1.8 mm was used assuming a medical tube having an inner diameter of 2 mm for pediatric use.
[0048]
First, a titanium oxide photocatalyst layer is coated on the inner surface, and a glass tube having super hydrophilicity with a contact angle with water of 1.3 degrees and surface modification with octadecyltriethoxysilane (ODS) to obtain a contact angle of 80.degree. The relationship between the volume of the injected bubble and the rising speed of the bubble was measured for the glass tube set at 6 degrees. As a result, as shown in FIG. 7, in the glass tube coated with the titanium oxide photocatalyst layer, bubbles rose and escaped, and the rising speed changed depending on the volume of the bubbles, but in the glass tube having a contact angle of 80.6 degrees, Bubbles never escaped regardless of the size. The bubble rising speed is usually considered to be faster because the buoyancy increases as the bubble volume increases, but showed a reverse trend as shown in FIG. This is thought to be due to resistance due to the difficulty of movement of the surrounding water, especially when bubbles rise, the water that appears above the bubbles needs to move to the bottom of the bubbles, It is considered that the increase rate decreases as the value increases. Further, the rising speed of the bubble is not a problem in practice, and it is considered that it is only necessary for the bubble to escape by its own buoyancy. If the volume of the bubble is about 2.5 μL or less, 1 cm Ascend at a sufficient speed of at least / sec. In reality, it is considered that it is often required to extract minute bubbles of 2 μL or less, and it is considered important to find the condition of the contact angle for extracting such bubbles. In FIG. 7, when the bubble volume is about 3.5 μL or more, the reason why the hydrophilic glass tube does not rise is that the size of the bubble is equal to or larger than the inner diameter of the glass tube, In this case, the bubbles cannot rise unless the water existing above the bubbles moves to the lower part of the bubbles. A device for extracting such a large bubble will be described later.
[0049]
Considering extraction of bubbles of 2 μL in a glass tube having an inner diameter of 1.8 mm as described above, the relationship between the water contact angle on the tube inner surface and the bubble rising speed is as shown in FIG. In this case, the absolute value of the bubble rising speed is not so important. In short, it is only necessary that the bubbles are detached from the inner surface of the tube and lifted up by buoyancy. When the tube is turned upside down, the bubbles that have started to move along the inner surface of the tube will eventually desorb from the inner surface of the tube, and thereafter rise as shown in FIG. 8 at a speed that is independent of the water contact angle on the inner surface of the tube. ing. However, if the water contact angle on the inner surface of the pipe is high, it may re-adhere, and for this purpose, the contact angle with water should be about 30 degrees or less or about 20 degrees or less. is important.
[0050]
All the bubbles inside the tube are lifted by buoyancy except that they stay attached to the inner surface of the tube, so whether or not the bubbles can escape is related to whether they can move away from the inner surface of the tube. The ease of separation from the inner surface of the tube is considered to be an important factor. Therefore, in the present invention, the easy bubble detachment index is defined and introduced as an index representing the ease of detachment from the inner surface of the tube. That is, in the present invention, a hydrophilic layer is formed on the inner surface of the elastomer tube, and this hydrophilic layer is filled with water in the tube and in the state where 2 μL of bubbles that contact the inner surface of the tube are present in the filled water. It is preferable that the easy bubble detachment index introduced as an index represented by the tube inclination angle at which the bubbles start to rise along the inner surface of the tube when the tube is tilted from the horizontal is 20 degrees or less, As a result, the bubbles can easily start to rise.
[0051]
This index was attempted to be quantified by the model test shown in FIG. As shown in FIG. 9, water (24 ° C.) is contained in a container 11, a glass substrate 12 made of a flat plate is submerged in the water and kept in a horizontal posture, and from therebelow a predetermined volume (test) 2 μL) of bubbles 14 are injected and held on the lower surface of the glass substrate 12, and when the glass substrate 12 is tilted, the inclination angle of the glass substrate 12 starts to move (starts rising). Stipulated as The relationship between this index and the contact angle of water on the inner surface of the tube is shown in FIG.
[0052]
The characteristic that the bubble separation index defined by the bubbles of 2 μL is 20 degrees or less and the bubbles start to move is almost the same as the hydrophilic characteristic that the contact angle with water on the inner surface of the tube is 20 degrees or less. Therefore, it can be said that the contact angle with water is 20 degrees or less and the easy bubble separation index is 20 degrees or less, which is a preferable characteristic with respect to the ease of separation of bubbles.
[0053]
Further, using the test apparatus shown in FIG. 9, the same test was performed on the infusion solution for infusion (20 ° C.) instead of water. The results are also shown in FIG. In infusion, the viscosity of the glass substrate changed slightly because of different viscosities, etc., but at a contact angle of 20 degrees, it was confirmed that the bubbles would surely start rising just by tilting the glass substrate slightly. It was done. As described above, the bubble rising speed is hardly a problem in reality, and the bubble can be extracted as long as the bubble can start to rise. Thus, when the water contact angle is set to 20 degrees or less, it has been confirmed that bubbles can be satisfactorily extracted.
[0054]
However, the inclination angle of the glass substrate 12 at which bubbles start to rise in the model test shown in FIG. 9 also depends on the size of the bubbles. In defining the easy bubble separation index, the size of the bubble was set to 2 μL. However, if the bubble becomes larger, it becomes as shown in FIG. That is, when the bubble becomes large, the bubble starts to rise from a shallow angle due to the increase in buoyancy. As can be seen from FIG. 11, the change in the inclination angle of the glass substrate 12 where the bubbles start to move begins to increase in the contact angle range of 20 to 40 degrees. It is understood that even a bubble having a size can be easily detached. Also from this aspect, it can be understood that the provision of a hydrophilic layer having a contact angle with water of 20 degrees or less on the inner surface of the elastomer tube as defined in the present invention is an extremely appropriate rule.
[0055]
In addition, when it is required to extract bubbles that are equal to or larger than the inner diameter of the tube, it is preferable to devise the following in addition to setting the inner surface of the tube to a contact angle of 20 degrees or less. In this case, as shown in FIG. 12, the bubbles 21 are formed in a vertically long shape in the longitudinal direction of the tube 22 and are easily held in the tube 22. However, as shown in FIGS. The ridges 23 made of, for example, can be stretched along the inner surface of the tube 22 in the longitudinal direction of the tube 22. The water at the upper part of the bubble 21 can easily move downward along the ridge 23 along the hydrophilic tube inner surface, so that the bubble 21 can also rise with the movement of the water. Although at least one ridge 23 functions, it is desirable to provide two or more. Instead of the ridges 23, as shown in FIG. 14, grooves that form the recesses 32 may be formed on the inner surface of the tube 31.
[0056]
In this way, basically, if the tube inner surface is hydrophilized so that the contact angle with water is 20 degrees or less, it is possible to easily and naturally extract the air bubbles mixed in the tube, and the air bubbles escape. Regarding the ease, it is also possible to refer to the easy bubble separation index. Further, as described above, it has also been explained that this performance can be realized by subjecting an elastomer as a tube material to extraction removal processing of a specific additive in advance and forming a predetermined titanium oxide photocatalyst layer thereon. Therefore, the elastomer tube realized in this way is extremely useful in various fields where air bubble removal is required, particularly in the medical field, and the air bubble removal work that has been conventionally performed is unnecessary or greatly reduced. The
[0057]
Based on the above knowledge, the silicone rubber catheter is actually subjected to the extraction and removal treatment of the additive with the above-mentioned mixed solution of n-hexane and acetone, and the titanium oxide photocatalyst layer is formed on the inner surface of the tube by the method described above. And strength 1mW / cm²We tried to make it hydrophilic by irradiating UV rays. The relationship between the ultraviolet irradiation time in this test and the water contact angle on the surface of the titanium oxide photocatalyst layer is shown in FIG. As shown in FIG. 15, it was possible to obtain super hydrophilicity with a water contact angle of 4 to 5 degrees by ultraviolet irradiation for about 10 hours or less.
[0058]
The superhydrophilic silicone rubber catheter was left in a dark place, and it was examined how much the titanium oxide photocatalyst layer on the inner surface of the tube became hydrophobic with time. The results are shown in FIG. As shown in FIG. 16, even after about 2 weeks, the contact angle with water is kept at 14 degrees or less, and sufficient hydrophilicity with a contact angle of 20 degrees or less targeted in the present invention is maintained. It was confirmed. As a result, it has been confirmed that a tube having a sufficiently defoaming performance can be obtained by the method of forming a hydrophilic layer on the inner surface of the tube as described above.
[0059]
【The invention's effect】
  As described above, according to the hydrophilic tube of the present invention and the method for producing the same, the elastomerAs silicone rubberBy providing a hydrophilic layer having a contact angle with water of 20 degrees or less on the inner surface of the tube body made of the above, it is possible to easily and naturally extract bubbles mixed in the tube, which is conventionally performed. The troublesome work of removing air bubbles can be eliminated or at least greatly reduced. In particular, in the medical field, the necessity and reduction of this work can not only contribute to a significant reduction in the burden on nurses and the like, but can also contribute to improving the certainty and reliability of medical care.
[Brief description of the drawings]
FIG. 1 is a relationship diagram between a contact angle with water and an ultraviolet irradiation time in a test using carbon tetrachloride.
FIG. 2 is a relationship diagram between contact angle with water and ultraviolet irradiation time in a test using acetone and hexane.
FIG. 3 is a contact angle characteristic diagram in a hydrophobicity confirmation test of an extract with an extractant.
FIG. 4 is a relationship diagram between a contact angle with water and an ultraviolet irradiation time in a test using a mixed solution of hexane and acetone as an extractant.
FIG. 5 is a diagram showing the results of a bubble adhesion test using carbonated water of a tube subjected to hydrophilic treatment and an untreated tube.
FIG. 6 is a schematic perspective view of a test apparatus for examining the ease of removal of bubbles in a tube.
7 is a relationship diagram between the bubble volume and the bubble rising speed showing the test result of FIG. 6; FIG.
8 is a relationship diagram between a contact angle with water and a bubble rising speed in the test of FIG.
FIG. 9 is a schematic perspective view of a simulation test apparatus using a flat plate for obtaining a relationship between a contact angle between a substrate and water and a substrate inclination angle at which bubbles start to rise.
FIG. 10 is a relationship diagram between a contact angle of the substrate with water and a substrate tilt angle at which bubbles start to rise.
FIG. 11 is a diagram showing the relationship between the contact angle of the substrate with water and the substrate tilt angle at which the bubbles start to rise when the bubble size is changed.
FIG. 12 is a schematic perspective view of a test apparatus showing an example when large bubbles are present in a tube.
13 is an enlarged cross-sectional view of the apparatus of FIG.
FIG. 14 is a schematic cross-sectional view of another test apparatus.
FIG. 15 is a graph showing the relationship between the ultraviolet irradiation time and the water contact angle when a titanium oxide photocatalyst layer is formed on a silicone rubber catheter from which an additive has been extracted and removed.
16 is a change characteristic diagram of water contact angle when the superhydrophilic silicone rubber catheter obtained in the test shown in FIG. 15 is left in a dark place.
[Explanation of symbols]
1 container
2 Glass tube
3 Bubble injection syringe
4 bubbles
11 containers
12 Glass substrate
13 Syringe for bubble injection
14 Bubbles
21 bubbles
22 tubes
23 ridges
31 tubes
32 concave

Claims (12)

It consists of a layer containing titanium oxide as a photocatalyst and light-irradiated on the inner surface of the tube body made of silicone rubber from which low molecular weight polydimethylsiloxane is extracted and removed using a mixture of n-hexane and acetone . A hydrophilic tube having an inner diameter of 2 mm or less, wherein a hydrophilic layer having a contact angle with water of 20 degrees or less is provided.   When the hydrophilic layer is filled with water in the tube and the tube is tilted from the horizontal in a state where 2 μL of air bubbles having a size of 2 μL in contact with the inner surface of the tube are present in the filled water, the air bubbles follow the inner surface of the tube. The hydrophilic tube according to claim 1, comprising a layer having an easy bubble detachment index represented by an inclination angle of the tube that starts to rise up to 20 degrees or less. The inner surface of the tube, at least one strip of ridges or concave extending in longitudinal direction of the tube is provided, the hydrophilic tube according to claim 1 or 2. Said tube is made of medical tubing, hydrophilic tube according to any one of claims 1-3. The hydrophilic tube according to claim 4 , wherein the medical tube is a tube for infusion or drug administration. The hydrophilic tube according to claim 4 , wherein the medical tube comprises a catheter for insertion or indwelling in a human body. It consists of a layer containing titanium oxide as a photocatalyst and light-irradiated on the inner surface of the tube body made of silicone rubber from which low molecular weight polydimethylsiloxane is extracted and removed using a mixture of n-hexane and acetone . A method for producing a hydrophilic tube having an inner diameter of 2 mm or less, wherein a hydrophilic layer having a contact angle with water of 20 degrees or less is formed. As the hydrophilic layer, when the tube is inclined from the horizontal in a state in which the tube is filled with water and a bubble having a size of 2 μL in contact with the tube inner surface is present in the filled water, the bubble follows the tube inner surface. The method for producing a hydrophilic tube according to claim 7 , wherein a layer having an easy bubble detachment index represented by an inclination angle of the tube starting to rise is 20 degrees or less. The method for producing a hydrophilic tube according to claim 7 or 8 , wherein at least one ridge or recess extending in the tube longitudinal direction is further formed on the inner surface of the tube. The manufacturing method of the hydrophilic tube in any one of Claims 7-9 whose said tube is a medical tube. The method for producing a hydrophilic tube according to claim 10 , wherein the medical tube is an infusion solution or a drug solution administration tube. The method for producing a hydrophilic tube according to claim 10 , wherein the medical tube is a catheter for insertion or indwelling in a human body.

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